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AUDIO SPOTLIGHTING

A technical seminar report submitted to JNTU KAKINADA

UNIVERSITY

In the partial fulfillment of requirements for the award of the degree of

bachelor of technology

In

ELECTRONICS AND COMMUNICATION ENGINEERING

Submitted By:

CH.PRANEETHA(08F01A0415)

Under the esteemed guidance

of

Mr.K.MADHU SUDHAN RAO, M.Tech.,

ASSISTANT PROFESSOR

Department of Electronics and communicating engineering

ST.ANN’S COLLEGE OF ENGINEERING&TECHNOLOGY,CHIRALA



ABSTRACT

Audio spot lighting is a very recent technology that creates focused beams of sound

similar to light beams coming out of a flashlight. By ‘shining’ sound to one location,

specific listeners can be targeted with sound without others nearby hearing it. It uses a

combination of non-linear acoustics and some fancy mathematics. But it is real and is

fine to knock the socks of any conventional loud speaker. This acoustic device comprises

a speaker that fires inaudible ultrasound pulses with very small wavelength which act in a

manner very similar to that of a narrow column. The ultra sound beam acts as an airborne

speaker and as the beam moves through the air gradual distortion takes place in a

predictable way due to the property of non-linearity of air. This gives rise to audiblecomponents that can be accurately predicted and precisely controlled. Joseph Pompei’s

Holosonic Research Labs invented the Audio Spotlight that is made of a sound processor,

an amplifier and the transducer. The American Technology Corporation developed the

Hyper Sonic Sound-based Directed Audio Sound System. Both use ultrasound based

solutions to beam sound into a focused beam. Audio spotlight can be either directed at a

particular listener or to a point where it is reflected.

The targeted or directed audio technology is going to a huge commercial market in

entertainment and consumer electronics and technology developers are scrambling to tap

in to the market. Being the most recent and dramatic change in the way we perceive

sound since the invention of coil loud speaker, audio spot light technology can do many

miracles in various fields like Private messaging system, Home theatre audio system,

Navy and military applications, museum displays, ventriloquist systems etc. Thus audio

spotlighting helps us to control where sound comes from and where it goes!



INTRODUCTION

JUST WHAT IS AUDIO SPOTLIGHTING?

Audio spot lighting is a very recent technology that creates focused beams of sound

similar to light beams coming out of a flashlight. By ‘shining’ sound to one location,

specific listeners can be targeted with sound without others nearby hearing it, ie to focus

sound into a coherent and highly directional beam. It uses a combination of non-linear

acoustics and some fancy mathematics. But it is real and is fine to knock the socks of any

conventional loud speaker. The Audio Spotlight & Hyper Sonic Sound Technology

(developed by American Technology Corporation), uses ultrasonic energy to create

extremely narrow beams of sound that behave like beams of light. Audio spotlighting

exploits the property of non-linearity of air. When inaudible ultrasound pulses are fired

into the air, it spontaneously converts the inaudible ultrasound into audible sound tones,

hence proved that as with water, sound propagation in air is just as non-linear, and can be

calculated mathematically. A device known as a parametric array employs the non-

linearity of the air to create audible by-products from inaudible ultrasound, resulting in an

extremely directive, beamlike wide-band acoustical source. This source can be projected

about an area much like a spotlight, and creates an actual specialized sound distant fromthe transducer. The ultrasound column acts as an airborne speaker, and as the beam

moves through the air, gradual distortion takes place in a predictable way. This gives rise

to audible components that can be accurately predicted and precisely controlled.

THEORY

IN TO THE DEPTHS OF AUDIO SPOTLIGHTING TECHNOLOGY

What ordinary audible sound & Conventional Loud Speakers lack? What we need?

About a half-dozen commonly used speaker types are in general use today. They range

from piezoelectric tweeters that recreate the high end of the audio spectrum, to various

kinds of mid-range speakers and woofers that produce the lower frequencies. Even the



most sophisticated hi-fi speakers have a difficult time in reproducing clean bass, and

generally rely on a large woofer/enclosure combination to assist in the task. Whether they

be dynamic, electrostatic, or some other transducer-based design, all loudspeakers today

have one thing in common: they are direct radiating-- that is, they are fundamentally a

piston-like device designed to directly pump air molecules into motion to create the

audible sound waves we hear. The audible portions of sound tend to spread out in all

directions from the point of origin. They do not travel as narrow beams—which is why

you don’t need to be right in front of a radio to hear music. In fact, the beam angle of

audible sound is very wide, just about 360 degrees. This effectively means the sound that

you hear will be propagated through air equally in all directions. In order to focus sound

into a narrow beam, you need to maintain a low beam angle that is dictated by

wavelength. The smaller the wavelength, the less the beam angle, and hence, the more

focused the sound. Unfortunately, most of the human-audible sound is a mixture of

signals with varying wavelengths—between 2 cms to 17 meters (the human hearing

ranges from a frequency of 20 Hz to 20,000 Hz). Hence, except for very low

wavelengths, just about the entire audible spectrum tends to spread out at 360 degrees. To

create a narrow sound beam, the aperture size of the source also matters—a large

loudspeaker will focus sound over a smaller area. If the source loudspeaker can be made

several times bigger than the wavelength of the sound transmitted, then a finely focused

beam can be created. The problem here is that this is not a very practical solution. To

ensure that the shortest audible wavelengths are focused into a beam, a loudspeaker about

10 meters across is required, and to guarantee that all the audible wavelengths are

focused, even bigger loudspeakers are needed.

Here comes the acoustical device “AUDIO SPOTLIGHT” invented by Holosonics Labs

founder Dr. F. Joseph Pompei (while a graduate student at MIT), who is the master brain

behind this technology.



FIG.1:-AUDIO SPOTLIGHT CREATES FOCUSED BEAM OF SOUND UNLIKE

CONVENTIONAL LOUD SPEAKERS

Audio spotlight looks like a disc-shaped loudspeaker, trailing a wire, with a small laser

guide-beam mounted in the middle. When one points the flat side of the disc in your

direction, you hear whatever sound he's chosen to play for you — perhaps jazz from a

CD. But when he turns the disc away, the sound fades almost to nothing. It's markedly

different from a conventional speaker, whose orientation makes much less difference.

FIG.2:- F.JOSEPH POMPEI AT THE MEDIA LAB OF THE MASSACHUSETTS

INSTITUTE OF TECHNOLOGY DEMONSTRATES HOW INVISIBLE ULTRASONIC

WAVES, AS ILLUSTRATED HERE, COULD HELP "STEER" SOUND.

(ABCNEWS.COM)

TECHNOLOGY OVERVIEW



The Audio Spotlight & Hyper Sonic Sound Technology (developed by American

Technology Corporation), uses ultrasonic energy to create extremely narrow beams of sound

that behave like beams of light. Ultrasonic sound is that sound that has very small

wavelength—in the millimeter range and you can’t hear ultrasound since it lies beyond the

threshold of human hearing.

COMPONENTS AND SPECIFICATIONS

Audio Spotlight consists of three major components: a thin, circular transducer array, a

signal processor and an amplifier. The lightweight, nonmagnetic transducer is about .5 inches

(1.27 centimeters) thick, and it typically has an active area 1 foot (30.48 cm) in diameter. It

can project a three-degree wide beam of sound that is audible even at distances over 100

meters (328 feet). The signal processor and amplifier are integrated into a system about the

size of a traditional audio amplifier, and they use about the same amount of power.

SOUND BEAM PROCESSOR/AMPLIFIER

• Worldwide power input standard

• Standard chassis 6.76”/171mm (w) x 2.26”/57mm (h)x 11”/280mm (d), optional rack

mount kit

• Audio input: balanced XLR, 1/4” and RCA (with BTW adapter) Custom configurations

available eg. Multichannel

AUDIO SPOTLIGHT TRANSDUCER



• 17.5”/445mm diameter, 1/2”/12.7mm thick, 4lbs/1.82kg

• Wall, overhead or flush mounting

• Black cloth cover standard, other colours available

• Audio output: 100dB max

• ~1% THD typical @ 1kHz

• Usable range: 20m

• Audibility to 200m

• Optional integrated laser aimer 13”/ 330.2mm and 24”/ 609.6mm diameter also

available

• Fully CE compliant

• Fully realtime sound reproduction - no processing lag

NON-LINEARITY OF AIR

Audio spotlighting exploits the property of non-linearity of air. When inaudible ultrasound

pulses are fired into the air, it spontaneously converts the inaudible ultrasound into audible

sound tones, hence proved that as with water, sound propagation in air is just as non-linear,

and can be calculated mathematically. A device known as a parametric array employs the



non-linearity of the air to create audible by-products from inaudible ultrasound, resulting in

an extremely directive, beamlike wide-band acoustical source. This source can be projected

about an area much like a spotlight, and creates an actual spatialized sound distant from the

transducer. The ultrasound column acts as an airborne speaker, and as the beam moves

through the air, gradual distortion takes place in a predictable way. This gives rise to audible

components that can be accurately predicted and precisely controlled. However, the problem

with firing off ultrasound pulses, and having them interfere to produce audible tones is that

the audible components created are nowhere similar to the complex signals in speech and

music. Human speech, as well as music, contains multiple varying frequency signals, which

interfere to produce sound and distortion. To generate such sound out of pure ultrasound

tones is not easy. This is when teams of researchers from Ricoh and other Japanese

companies got together to come up with the idea of using pure ultrasound signals as a carrier

wave, and superimposing audible speech and music signals on it to create a hybrid wave. If

the range of human hearing is expressed as a percentage of shift from the lowest audible

frequency to the highest, it spans a range of 100,000%. No single loudspeaker element can

operate efficiently or uniformly over this range of frequencies. In order to deal with this

speaker manufacturers carve the audio spectrum into smaller sections. This requires multiple

transducers and crossovers to create a 'higher fidelity' system with current technology.

FIG.3:-PARAMETRIC LOUDSPEAKER- AMAZING AUDIO SPOTLIGHT

(Airborne ultrasounds of 28kHz are envelope-modulated with audio signals. Inherent

non-linearity of the air works as a de-modulator. Thus de-modulated sounds impinge on our



eardrums. We can hear those sounds! )

Using a technique of multiplying audible frequencies upwards and superimposing them on a

"carrier" of say, 200,000 cycles the required frequency shift for a transducer would be only

10%. Building a transducer that only needs to produce waves uniformly over only a 10%

frequency range. For example, if a loudspeaker only needed to operate from 1000 to 1100 Hz

(10%), an almost perfect transducer could be designed.

FIG.4:-SHOWING THE DIFFERENCE IN MODULATING AUDIBLE FREQUENCIES

WITH ULTRASONIC CARRIER

This is similar to the idea of amplitude modulation (AM), a technique used to broadcast

commercial radio stations signals over a wide area. The speech and music signals are mixed

with the pure ultrasound carrier wave, and the resultant hybrid wave is then broadcast. As

this wave moves through the air, it creates complex distortions that give rise to two new

frequency sets, one slightly higher and one slightly lower than the hybrid wave. Berktay’s

equation holds strong here, and these two sidebands interfere with the hybrid wave and

produce two signal components, as the equation says. One is identical to the original sound

wave, and the other is a badly distorted component. This is where the problem lies—the

volume of the original sound wave is proportional to that of the ultrasounds, while the

volume of the signal’s distorted component is exponential. So, a slight increase in the

volume drowns out the original sound wave as the distorted signal becomes predominant. It



was at this point that all research on ultrasound as a carrier wave for an audio spotlight got

bogged down in the 1980s. Focusing on the signal’s distorted component, since the signal

component’s behavior is mathematically predictable, the technique to create the audio beam

is simple; modulate the amplitude to get the hybrid wave, then calculate what the Becktay’s

Equation does to this signal, and do the exact opposite. In other words, distort it, before

Mother Nature does it Finally, pass this wave through air, and what you get is the original

sound wave component whose volume, this time, is exponentially related to the volume of

the ultrasound beam, and a distorted component, whose volume now varies directly as the

ultrasound wave. By creating a complex ultrasound waveform (using a parametric array of

ultrasound sources), many different sources of sound can be created. If their phases are

carefully controlled, then these interfere destructively laterally and constructively in the

forward direction, resulting in a collimated sound beam or audio spotlight. Today, the

transducers required to produce these beams are just half an inch thick and lightweight, and

the system required to drive it has similar power requirements to conventional amplifier

technology.

FIG.5:-COMPUTER SIMULATION OF SOUND PROPAGATION: COMPLEX SET OF

HIGH-INTENSITY ULTRASOUND SIGNALS INTERMODULATEAIR. AMONG THE

PRODUCTS IS A COLLIMATED AUDIO "SPOTLIGHT".

DIRECT AUDIO AND PROJECTED AUDIO

There are two ways to use Audio Spotlight. First, it can direct sound at a specific target,

creating a contained area of listening space which is called “Direct Audio”. Second, it can

bounce off of a second object, creating an audio image. This audio image gives the illusion

of a loudspeaker, which the listener perceives as the source of sound, which is called

“projected Audio”. This is similar to the way light bounces off of objects. In either case, the



sound’s source is not the physical device you see, but the invisible ultrasound beam that

generates it

FIG.6:- DIRECT AUDIO AND PROJECTED AUDIO

Hyper Sonic Sound technology provides linear frequency response with virtually none of the

forms of distortion associated with conventional speakers. Physical size no longer defines

fidelity. The faithful reproduction of sound is freed from bulky enclosures. There are no,

woofers, tweeters, crossovers, or bulky enclosures. Thus it helps to visualize the traditional

loudspeaker as a light bulb, and HSS technology as a spotlight, that is you can direct the

ultrasonic emitter toward a hard surface, a wall for instance, and the listener perceives the

sound as coming from the spot on the wall. The listener does not perceive the sound as

emanating from the face of the transducer, only from the reflection off the wall.

Contouring the face of the HSS ultrasonic emitter can tightly control Dispersion of the audio

wave front. For example, a very narrow wave front might be developed for use on the two

sides of a computer screen while a home theater system might require a broader wave front

to envelop multiple listeners.



FIG.7:-CONVENTIONAL LOUDSPEAKER & ULTRASONIC EMITTER

SPECIAL FEATURES OF AUDIO SPOTLIGHT

A COMPARISON WITH CONVENTIONAL LOUD SPEAKER:-

• Creates highly FOCUSED BEAM of sound

• Sharper directivity than conventional loud speakers using Self demodulation of finite

amplitude ultrasound.

• with very small wavelength as the carrier.

• Uses inherent non-linearity of air for demodulation.

• Components- A thin circular transducer array, a signal processor & an amplifier.

• Two ways to use- Direct & projected audio

• Wide range of applications

• Highly cost effective



APPLICATIONS OF AUDIO SPOTLIGHTING -TOWARDS THE

FUTURE

"So you can control where your sound comes from and where it goes," says Joe

Pompei, the inventor of Audio Spotlight. , Pompei was awarded a “Top Young Innovator”award from Technology Review Magazine for his achievements.

The targeted or directed audio technology is going to tap a huge commercial market in

entertainment and in consumer electronics, and the technology developers are scrambling to

tap into that market. Analysts claim that this is possibly the most dramatic change in the way

we perceive sound since the invention of the coil loudspeaker. The technology that the

Holosonics Research Labs and the American Technology Corporation are lining up may

seem to be a novelty of sorts, but a wide range of applications are being targeted at it.

Continuing to improve on the commercial success of the Audio Spotlight sound system,

Holosonics has announced that its next-generation laser-like sound system, with improved

performance and lower cost, is now actively in production. These new systems are being

exhibited at the 2004 Consumer Electronics Show in Las Vegas alongside MIT Media Lab

technology.

The performance and reliability of the Audio Spotlight have made it the choice of the

Smithsonian Institution, Motorola, Kraft, and Cisco Systems etc.

Holosonics put in four individual Audio Spotlights into the Daimler Chrysler

MAXXcab prototype truck to let all the passengers enjoy their own choice of music. Boston

Museum of Science - as well as the United States military.

There is an even bigger market for personalized sound systems in entertainment and

consumer electronics.

Holosonic Labs is working on another interesting application at the Boston Museum



of Science that allows the intended listeners to understand and hear explanations, without

raising the ambient sound levels. The idea is that museum exhibits can be discretely wired up

with tiny speaker domes that can unobtrusively, provide explanations.

There are also other interesting applications that they are looking at, such as private

messaging using this system without headphones special effects at presentations as well as

special sound theme parks that could put up animated sound displays similar to today’s light

shows. Holosonic has installed their Audio Spotlight system at Tokyo’s Sega Joyopolis

theme park.

The US Navy has installed sound beaming technology on the deck of an Aegis-class

Navy destroyer, and is looking at this as a substitute to the radio operator’s headphones.

CONCLUSION

“Being the most radical technological development in acoustics since the coil loudspeaker

was invented in 1925... The audio spotlight will force people to rethink their relationship

with sound…”

-NewyorkTimesSo we can conclude- Audio Spotlighting really “put sound where you want it” and will be “A

REAL BOON TO THE FUTURE.”



REFERENCES

www.thinkdigit.com

www.holosonics.com

www.spie.org

www.howstuffworks.com

www.abcNEWS.com

ENGINEERING PHYSICS By B.PREMLET

UNIVERSAL PHYSICS

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